November 3, 2014

Case for completing reservoir drain pipe not water tight

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The City of Aspen's Leonard M. Thomas Reservoir, perched on a hillside above lower Castle Creek Road, holds 10 acre feet of water.

Jordan Curet/Aspen Daily News

The City of Aspen's Leonard M. Thomas Reservoir, perched on a hillside above lower Castle Creek Road, holds 10 acre feet of water.

Thomas Reservoir, with the Aspen water treatment plant in the background.

David Hornbacher / City of Aspen

Thomas Reservoir, with the Aspen water treatment plant in the background.

ASPEN – David Hornbacher, the city of Aspen’s director of utilities, acknowledged Friday he may have oversold the impact of a May 27 state dam safety report to the city council on Oct. 21, when he successfully convinced elected officials at a budget work session to approve $750,000 to complete the tail end of a big pipeline running from the bottom of Leonard Thomas Reservoir toward Castle Creek.

Hornbacher left the council with the distinct impression that the state was now requiring the city to complete the pipeline, originally envisioned as a penstock to a proposed hydropower plant, and now primarily seen as an “emergency drain line” for the city reservoir.

But, as it turns out, the state is not specifically requiring the city to finish its big pipeline, nor has it ever told the city the pipeline is required to safely operate the reservoir.

Erin Gleason is the state dam safety engineer with the Colorado Division of Water Resources who inspected the dam and reservoir in May. She wants documentation that the city can slowly draw down the reservoir through its existing low level outlet, which today directly feeds the city’s adjoining water treatment plant, or whether a bypass of the plant will be required.

“It might just be that I need information,” Gleason said.

After talking with Gleason on Friday, Hornbacher said he now intends to research whether the city can meet Gleason’s concerns by either using the reservoir’s current low-level outlet system, or if it can do so after some level of modification. He said he would prepare a range of options that compare cost and risk and bring them to council to discuss.

Hornbacher also said he would clarify things by describing two types of potential emergencies at the reservoir. The first is some type of structural threat to the dam, which would require the use of a low-level outlet to slowly draw down the reservoir. The proposed emergency drain line, if finished, would serve as a low-level outlet.

The second type is a a hydrologic event, such as losing control of the two feeder pipes that can bring up to 52 cfs of water to the reservoir, which requires the use of a spillway or an emergency drain line to deal with more water coming into the reservoir than it has the capacity to contain.

“We look forward to having a greater depth of discussion to solutions to a low-level outlet and a hydrologic event, and we look forward to a follow-up to have a detailed discussion about the options,” Hornbacher said.

Hornbacher said on Friday that he did not try to mislead the city council about the reservoir.

“My intent is to try and be factual and accurate and convey the information in an open and honest way,” Hornbacher said, pointing out that his answers were to questions at a budget work session, and he did not make a formal proposal.

And it’s fair to note that it is Hornbacher’s standing professional opinion that the city should complete the last 360 feet of the 4,000-foot-long pipeline installed before the proposed hydropower project ran into political turmoil and was mostly shelved by the city council.

He has consistently pointed out that the pipeline is a better way to move a lot of water out the reservoir than running it down the hillside just to the east of the reservoir. However, the city does routinely run 3 to 4 cubic feet per second (cfs) of water down the hillside toward the creek, but Hornbacher is concerned that a flow of 52 cfs could damage Castle Creek Road.

A water tight case?

At an Oct. 21 budget work session, Hornbacher was asked by council to answer questions about the $750,000 line item in the 2015 budget. (On meeting video, start at 26:52).

There was no staff memo on the topic and the May 27 dam inspector’s report was not in the public packet, nor was the last inspector’s report from April 2012.

However, the discussion turned toward the May report from Gleason.

“The report requires that we complete, or provide some level of a low-level drain line, or outlet, to this reservoir,” Hornbacher told the council. “Completing the drain line does provide that low-level outlet to the reservoir. So we do have an action item required by the dam safety division. If we do not comply with that in a method that is acceptable to them, then they are forced to take action. “

At another point, Hornbacher told the council, “We need a have plan in place, something that we can demonstrate within the next several years, 2017, that you know, we’ve got something already done or that we’re taking this tangible action,” Hornbacher said. “And certainly completing the drain line is that action. If we were to try to look at other mechanisms, that would either require us to make modifications at the reservoir or provide other types of facilities that could drain that reservoir.”

With that, and other statements, Hornbacher consistently backed-up to his professional recommendation that the city complete the pipeline. And he only mentioned in passing the existing low level outlet.

During public comment at city council on Oct. 27, Maurice Emmer, a former Aspen mayoral candidate and staunch opponent of the city’s hydro project, told the council that they should conduct their own research and not trust staff to give them all the information they might need to make a decision on projects such as Thomas Reservoir.

“Staff makes a proposal, then it gives city council information to support the proposal,” Emmer said. “It doesn’t give council information that might undercut the proposal.” (Meeting video starts at 19:01).

For example, Emmer pointed out that Hornbacher did not tell council that the dam had been inspected in 2012, or elaborate on how the existing low-level outlet might satisfy the state.

And Hornbacher did not know, when asked by Councilman Dwayne Romero, how often the state inspects dams.

“I was going to look that up and I didn’t,” Hornbacher said. “I would say it is somewhere between two to five years, I’m thinking it’s around three, which is why you know, we’ve got this report in 2017.”

The state historically has inspected dams classified as “high hazard” dams, which pose a threat to human life, every year. It inspects significant hazard dams, which only pose a threat to property, every other year, as in 2012 and 2014 in the case of Thomas Reservoir, which has been classified as a significant hazard dam since at least 2012.

It’s not clear why Hornbacher is citing a need to act by 2017, as Gleason, the dam inspector, said she would need proof of a low-level outlet by the next inspection, which is slated for 2016.

Hornbacher, when asked, also did not cite the date of the last dam inspection, which was April 4, 2012.

Thomas Leonard Reservoir was completed in 1966, although water had historically been stored on the site in wooden structures to feed an old hydro plant in the same location as the proposed plant.

In 1989, the state concluded the city’s dam was under 10 feet tall, and didn’t meet its definition of a “jurisdictional” dam. So they stopped inspecting it. At the time it was classified as low hazard dam.

Inspection reports in the early 1980s mention that the reservoir’s low-level outlet drains to the water treatment plant — and was considered acceptable.

In 2010, when the city went to install its new penstock/emergency drain line, it had to rebuild the north side of the reservoir to a height of 19 feet, which put the dam back under the state’s jurisdiction.

At that time, regulators saw that the dam, if breached, would damage some property below the reservoir, but not threaten any lives, and gave it a significant hazard classification. That did not change at the May inspection, as Hornbacher implied on Oct. 21.

As to the overall damage that would be caused if the dam failed, a 2011 report by the city’s consulting engineers, McLaughlin Water Engineers, stated that “it is unlikely that buildings or roads would receive extensive damage as a result of a dam breach at Leonard Thomas Reservoir.”

No other options?

By the time Hornbacher was through discussing the completion of the emergency drain line with council on Oct. 21, it was clear he had persuaded them that his proposal was the only safe and correct course of action for the city to take to meet the requirements of the May inspection report.

“So, summing it up for my purposes, this is a state-mandated action to put in this drain line?” Councilman Art Daily asked Hornbacher at the end of the discussion on Oct. 21.

In response to Daily, who is an attorney with Holland and Hart, Hornbacher seemed to choose his words carefully.

“The state mandates that we must have a low-level outlet,” Hornbacher said. “What we have available is a nearly completed low-level outlet, and that would meet the state requirements. So they are telling you, you have to do it. They don’t necessarily go and say this, this and this, is how.”

“But some sort of drain line has got to go in?” Daily asked.

“Yep, a low-level outlet has got to be established in there for emergency, you know, release of water or draining the reservoir,” Hornbacher said.

“I guess, then the last question that comes to my mind is, are there any more equally efficient but more cost effective means of resolving the state requirement versus … this is the best solution?” Daily asked.

“This is a really enduring and complete solution, and by that I mean that you’ve got this hardened route that takes it to the stream and empties into the stream without further erosion or damage there at the stream, you’ve sort of dissipated the energy,” Hornbacher said. “Any other option that you might pursue to get water out of that reservoir does not have such a direct route, so you’d be either placing that water in an unimproved, sort of drainage-like way, and movement of such water would then … start to erode, and cause other types of damage, and then … basically recovery costs or other impacts we can’t even foresee today.”

However, it is also possible that there may be simpler and less expensive ways to meet the state’s requirements for a low-level outlet, without completing the emergency drain line — which the state has never required the city to install. And that’s what Hornbacher said on Friday he is now looking into.

In fact, as Hornbacher briefly alluded to early in his remarks on Oct. 21, and confirmed on Friday, there is a low level outlet already in place at the reservoir, and it sends water to the water treatment plant, where it can then be released down to Castle Creek.

All the state is requiring of a low-level outlet at Thomas Reservoir is that it be able to move 1 cubic feet per second (cfs) of water out of the reservoir over a five-day period, which would lower the water level by five feet — a state standard that technically doesn’t even apply to reservoirs as small as Thomas Reservoir.

Under the “Outlet” section of her May 27 dam inspection report, Gleason wrote “it is our understanding that the only active outlet(s) discharge into the water treatment plant. According to Rule 5.9.6.2.1, a low-level outlet is required to draw down the reservoir under emergency conditions. Please either provide documentation of an existing bypass for treatment plant flows, or provide a low level outlet for the reservoir.”

May was the first time Gleason had inspected Thomas Reservoir. She inspected another 60 dams this summer and said she will review issues identified in those inspections throughout the winter.

As a state dam safety engineer, Gleason said she has wide latitude to work with dam owners, such as the city, to come up with reasonable solutions to concerns raised during inspections.

According to a safety manual published by the state in 2002, “follow-up of the inspection often includes reviewing questionable conditions on site with the dam owner, explaining the problems and suggesting the best and/or most economical way to proceed in assuring the dam’s safety. Frequently, further studies by a consulting engineer are recommended.”

“We work with the owner to make sure we are not requiring something that they can’t afford,” Gleason said. “The city could propose having a stand-by generator, a pump and a hose on site. Our office would typically accept such a solution.”

Hornbacher, in his response to Daily or other council members, did not bring up the pump-and-hose option.

Editor’s note: The Aspen Daily News collaborated with Aspen Journalism on this story and published in Monday, Nov. 3, 2014. Aspen Journalism was responsible for an error in the printed version of the Daily News story, as well as the initial digital version, as we said David Hornbacher is a licensed engineer, and he is not.

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